In Bacillus subtilis the initiation of sporulation by partial deprivation of amino acids was examined. Stringent cells, showing the stringent response to amino acid deprivation; i.e., accumulating ppGpp, sporulated during partial amino acid (methionine) deprivation, whereas the relaxed strain did not. However, this was due to the associated GTP decrease because the relaxed strain could also sporulate upon addition of decoyinine, an inhibitor of GMP synthetase. In the yeast Saccharomyces cerevisiae, metabolic changes and sporulation were measured during conditions of nitrogen and carbon limitation. It was also determined why yeast cells grown in glucose can subsequently not grow on acetate, although they can grow on ethanol.